We use cookies to enhance your experience on our website. By continuing to use our website, you are agreeing to our use of cookies. You can change your cookie settings at any time.ContinueFind out more
1Astronomy A circle on the celestial sphere parallel to the horizon; a parallel of altitude.
‘It does both principle-plane and almucantar sky-radiance scans, which are then processed through sophisticated inversion techniques.’
‘It can be programmed to collect data in manual or automated sequences of measurements, which include almucantar and principal plane scenarios.’
‘To improve the accuracy of the scattering optical thickness, the inversion results are acceptable only if the radiance is measured across the total almucantar and is accurately fitted by a theoretical model.’
‘Once you have located the sun on the ecliptic, simply align the sun with the eastern horizon and read its position using the almucantars, which are drawn every ten degrees.’
‘The circles are almacantars (loci of constant elevation), spaced at 10° intervals; radial distance is proportional to cos (elevation angle).’
2A telescope mounted on a float resting on mercury, used to determine stellar altitude and azimuth.
‘The discovery, in 1891, of the variation of latitude by Seth Carlo Chandler Jr. depended in part upon Chandler's invention of the almucantar.’
‘It had been invented by a professor at Harvard, but Howe's version of it was much more imposing; the almucantar at Harvard Observatory weighed 35 pounds -- Howe's, 2,300 pounds.’
‘The pedestal of this almucantar is an ordinary cast-iron gaspipe, about 9 in. in diameter externally, and 6 ft. long, sunk 3 ft. in the ground.’
Origin
Middle English: from medieval Latin almucantarath or obsolete French almucantara, from Arabic al-muqanṭarāt ‘lines of celestial latitude’, based on al ‘the’ + qanṭara ‘arch’.